Most of polymerizable compounds known hithertofore undergo positive shrinkage in volume on polymerization. Thus, for example, ethylene, vinyl chloride, methyl methacrylate and styrene gives rise to a calculated shrinkage of about 15% to 66% during the addition polymerization (see William J. Bailey "J. Macromol. Sci. Chem." A9(5) pp. 849-865 (1975)). In cationic ring-opening polymerization of epoxides, considerable shrinkage in volume will occur, although the degree of shrinkage in that case is often less than that observed during the addition polymerization of the vinyl compounds. By way of reference, calculated shrinkages of some epoxides on the ring-opening polymerization are 23% for ethylene oxide; 17% for propylene oxide; 9% for styrene oxide; 12% for epichlorohydrin; and 20% for 2,2-dimethylethylene oxide. The calculated shrinkage in volume under discussion is given by the following equation: ##EQU1##
With such known monomers that will polymerize with an appreciable shrinkage in volume, there are problems that they provide no dimensional accuracy when used as molding materials, and that where used as casting materials, they impose strains due to the shrinkage on castings and cause reduction in adhesion to a mold as well as inaccuracy of the dimension of the castings. There are further problems in use that such monomers may lead to reduction in cohesion to a substrate or formation of warpage due to the internal strains when used as paints or adhesives.
Therefore, for a number of industrial applications including precision castings, strain-free composites, paints and adhesives, it is highly desirable to have curable materials which will present nearly zero change in volume on polymerization.
Certain bicyclic monomers which may polymerize with expansion in volume have been reported by William J. Bailey as described in the afore-mentioned literature (J. Macromol. Sci. Chem.). According to the literature, the spiro orthocarbonate of the formula: ##STR1## indicates a positive expansion of 2 to 17% upon its ring-opening polymerization.
We have extensively researched in an attempt to provide a new curable material which will polymerize and cure with no substantial change in volume. As a result, we have now succeeded to produce a new curable material which brings about substantially neither expansion nor shrinkage in volume on polymerization and curing and which may be produced in a facile way by reacting commercially available known compounds with a new compound, 1-alkyl-4-hydroxymethyl-2,6,7-trioxabicyclo[2,2,2]octane now synthetized by the present inventors.
An object of this invention is to provide a new curable material which polymerizes and cures with substantial no change in volume and hence is useful as moulding materials for manufacture of various articles, and particularly shaped articles by precision-casting technique and also useful as the material for use in adhesives and paints. Another object is to provide a process for the production of such new curable material which is conducted in a facile way. Further objects of this invention will be clear from the following descriptions.